In the field of a display panel provided in, e.g., a liquid crystal display device, there is a demand for a technique for improving visibility of the display panel when the display panel is viewed at an angle, for the purpose of improving a viewing angle.
Patent Literature 1 describes a liquid crystal display device including (i) a liquid crystal panel including a large number of pixels including a first pixel group and a second pixel group and (ii) a data driving section for respectively providing the first pixel group and the second pixel group with tone voltages corresponding to a first data signal and a second data signal that are for different gamma constants.
However, the conventional technique described in Patent Literature 1 involves a problem of displaying an image that is not an image desired to be displayed.
With reference to FIGS. 21 and 22, the following describes an example where a geometric pattern showing a black oblique line, for example, is displayed as a result of driving of the pixels according to the above-described conventional technique. FIG. 21 illustrates a display region of a conventional display device. FIG. 22 illustrates an image that is to be displayed in the display region shown in FIG. 21 but is not yet displayed by driving the pixels according to gamma curves having gamma characteristics being different for different pixels, that is, an image which is an original image to be displayed.
A display region 330 shown in FIGS. 21 and 22 includes a plurality of pixels 331 arranged in stripes. The description here deals with a configuration in which each of the pixels 331 is constituted by four sub pixels 341, 342, 343, and 344 displaying red (R), green (G), blue (B), and white (W), respectively.
The following method is considered as an example of the driving method carried out according to the above-described conventional technique, i.e., according to the gamma curves having different gamma characteristics for different pixels: As shown in FIG. 22, each of adjacent ones of the pixels 331 is driven with use of (i) a gamma curve having a gamma characteristic having a high (bright) relative luminance for each tone and (ii) a gamma curve having a gamma characteristic having a low (dark) relative luminance for each tone. However, with this method, there occurs a case where all pixels 331 located in positions (indicated by dotted-line rectangles in FIG. 22) corresponding to the oblique line that is to be displayed are driven according to the gamma curve having the bright gamma characteristic. This leads to a problem of failing to display the oblique line that is to be displayed.
Further, the sub pixels displaying different colors have different viewing angle characteristics and different chromaticity characteristics. This leads to a problem that a color is viewed differently (color deviation) between a case where the display region is viewed from the front and a case where the display region is viewed at an angle. FIG. 19 illustrates a positional relationship between (i) a case where the display region 330 is viewed from the front (front viewing) and (ii) a case where the display region 330 is viewed at a viewing angle of 60° (viewing at 60°). FIG. 20 illustrates RGBW tone characteristics observed when the display region of the conventional display device is viewed at a viewing angle of 60°, the conventional display device being adjusted so that its RGBW tone characteristics observed when the display region is viewed from the front become closer to a gamma curve C10 (γ=2.2) that is observed at a gamma characteristic of 2.2. Note that, in FIG. 20, a curve C11 indicates an R tone characteristic, a curve C12 indicates a G tone characteristic, a curve C13 indicates a B tone characteristic, and a curve C14 indicates a W tone characteristic.
As shown in FIG. 20, even in the case where the RGBW tone characteristics observed when the display region is viewed from the front are adjusted so as to be equal to each other, the RGBW tone characteristics observed when the display region is viewed at an angle become different. As is clear from this, the sub pixels displaying different colors have different viewing angle characteristics and different chromaticity characteristics.
In order to solve the problem of the color deviation in the above-described conventional technique, driving the sub pixels with use of the gamma curves individually adjusted for all the colors may be possible. However, this method involves another problem of making a configuration of an image processing section complicated.
With reference to FIG. 23, the following describes an image processing section employing the method of driving the sub pixels with use of the gamma curves individually adjusted for all the colors. FIG. 23 is a block diagram illustrating a configuration of an image processing section 322 in the conventional display device.
The image processing section 322 includes an RGBW developing section 351 and a tone characteristic adjusting section 352. The RGBW developing section 351 generates, from RGB data received from a video data processing section (not shown), red data (hereinafter, abbreviated as “R data”), green data (hereinafter, abbreviated as “G data”), blue data (hereinafter, abbreviated as “B data”), and white data (hereinafter, abbreviated as “W data”).
The tone characteristic adjusting section 352 includes an R data processing section 353, a G data processing section 354, a B data processing section 355, and a W data processing section 356. The R data processing section 353 carries out a process of generating adjusted R data from the R data generated in the RGBW developing section 351 in order that the sub pixels for displaying red are driven according to a gamma curve individually adjusted for the sub pixels for displaying red. In a similar manner, the G data processing section 354 processes the G data, the B data processing section 355 processes the B data, and the W data processing section 356 processes the W data.
Thus, in order to drive the sub pixels with use of the gamma curves individually adjusted for all the colors, individual adjustments for RGBW are necessary. This increases a circuit scale in the image processing section, thereby leading to additional problems of, e.g., an increase in the cost and an increase in the power consumption.